1. Field of the Invention
This invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium which exhibits excellent surface smoothness and low noise characteristics and which is extremely resistant to damage when it is moved in a video tape recorder for long-term in recording in the form of a thin magnetic tape.
2. Description of the Prior Art
In order to increase the information recording capacity of a magnetic tape for use in a video tape recorder, it is generally desired to minimize the thickness of the magnetic tape since the tape roll diameter in a video tape recorder is limited to a certain value. However, a magnetic tape of a reduced thickness presents a very real problem with regard to mechanical strength. Namely, if the tape thickness is reduced, the magnetic tape becomes limp and is readily stretched and damaged when it is moved in a video tape recorder.
Further, a video tape should have a small coefficient of friction to facilitate its movement over the fixed magnetic head, drum, guide pole and other components in a video tape recorder. A video tape having a large coefficient of friction suffers from a large movement tension and tends to be damaged in a video tape recorder. By tape damage is meant the elongation, deformation and edge folding of the magnetic tape which occur when the magnetic tape is used for recording and reproduction in a video tape recorder. Although tape damage occurs during normal movement of the magnetic tape, it occurs even more readily during loading and unloading thereof. This is because the magnetic tape receives a larger tension during loading and unloading than during normal movement. The magnetic tape is more readily damaged in the VHS system video tape recorder than in the .beta.-format system video tape recorder. As an example of a VHS system video tape recorder in which folding of the tape edges occurs readily there can be mentioned one in which the loading post is made of an acetal copolymer and in which the winding-up torque at the time of unloading is about 300 g-cm or more, as in the case of the Victor HR3600 (available from Victor Company of Japan, Limited), the MACLORD NV-8300 (available from Matsushita Electric Industrial Co., Ltd., in Japan), or the like. Folding of the tape edges occurs at a loading post 1 on the supply side as shown in FIG. 1 because of deterimental shifting of the magnetic tape along the loading posts 1 and 2. In this case, the surface (non-magnetic layer surface) of the tape opposite to the magnetic layer surface thereof is in contact with the loading posts.
The aforesaid tape damage causes skew, jitter and voice deterioration, and the tape edge folding seriously affects the magnetic recording and reproduction. Thus, a need exists for a magnetic recording tape which is highly resistant to the tape damage as described above.